1. Field of the Invention
The present invention relates to a multi-plate clutch, and more particularly to a multi-plate clutch having a hub member which engages an input shaft of a transmission, where the hub member is axially displaceable and axial displacement of the hub member is limited by the configuration of the multi-plate clutch.
2. Description of the Related Art
In general, a multi-plate clutch used in a racing car or the like is provided with a first cylindrical portion that is configured to be attached to a flywheel. Within the first cylindrical portion, a hub flange is disposed, the hub flange being connected to an input shaft of a transmission. At an outer radial portion of the hub flange, the hub flange is formed with a second cylindrical portion disposed radially inwardly of the first cylindrical portion. Drive plates and driven plates are disposed between the first and second cylindrical portions and directly engage each, respectively. A pressure plate mechanism is attached to the first cylindrical portion for selectively engaging and disengaging the drive plates and driven plates from rotation with the flywheel. The pressure plate mechanism includes a pressure plate and a diaphragm spring for biasing the pressure plate.
The hub flange has gear teeth formed on an outer circumferential surface of the second cylindrical portion and spline grooves formed on an inner circumferential portion. The outer circumferential gear teeth engage corresponding teeth formed on the driven plates, and the inner circumferential spline grooves engage spline teeth formed on the input shaft of the transmission.
The hub and the driven plates both may undergo movement in the axial direction when the clutch is in a clutch dis-engaged state in order to prevent drag between relatively rotating parts in clutch mechanism, such as the driven plates and the drive plates. However, in the absense of some kind of movement restriction, the hub would come loose from the splines on the input shaft if it moves too far in the axial direction. It is therefore necessary to provide some structure which limits the axial movement of the hub. One such known structure includes roll pins that are mounted on the outer circumferential spline of the hub flange and which extend in a tangential or radial direction. A portion, exposed in the gear teeth, of each roll pin estends between adjacent two teeth of the driven plates in the axial direction. The axial movement of the driven plates and the drive plates are limited by the flywheel and the pressure plate. The hub flange is engaged in the axial direction through the above-mentioned roll pin with the driven plates whose movement range is thus limited so that the axial position of the hub flange is limited within a predetermined range.
In the above-described configuration, since the roll pins are provided only at a couple of predetermined locations, the pressure against the driven plates in the area of contact therebetween is significant enough so that a frictional wear due to contact is likely to occur in the driven plates.
As well, when the torque is transmitted through the drive plates and the driven plates, slippage between the plates generates heat. The service life of the plates and other engaging parts is reduced by the heat. In order to cool the plates, in a conventional manner, slits or holes are formed in the first and second cylindrical portions. Air is caused to flow from the inner circumferential side to the outer circumferential side of both plates to thereby cool both plates.
However, the entrainment of the air from the outside of the clutch is limited. Air usually can only enter via the slit portions of the diaphragm spring. These slits are insufficient to permit the flow of air from the outside.
It is well known in the prior art to use two diaphragm springs in an overlap manner. In this case, when the two diaphragm springs are flexed, a friction is generated therebetween. This means that the flex-load characteristics have an increased hysteresis load due to the friction. As a result, an efficiency is degraded. Therefore, in order to enhance the lubricant effect between the diaphragm springs, a solid lubricant film is formed one of the contacting surfaces. However, since only one surface of each of the two diaphragm springs is subjected to a lubricant treatment, it is necessary to confirm which surface has the film prior to assembly. This requires an additional step in the assembly process, specifically the step of inspecting the surfaces of the two diaphragm spring to see which face has the film thereon.